Conventional electronics architectures usually consists in a logic controller chip (e.g. microcontroller, FPGA) and several power chips connected to the logic controller using serial or parallel data lines. In the automotive field, for example, an electronic control unit (ECU) is used to control the internal combustion engine. The microcontroller inside the ECU receives input signals from sensors associated with the internal combustion engine and generates output signals to different devices, as for example driving circuits of actuators provided to control the operation of the internal combustion engine.
The connection from the logic controller and the power chips using parallel lines (one for each output) can be critical for the very large number of lines requested and constrains in the logic controller package and related pin numbers; the use of the most serial line protocols (e.g. SPI) can be critical for the output latency. The introduction of the microsecond channel bus (MSC) solves many of the issues stated above and it is already implemented in the most diffused microcontrollers used in the automotive, as well as is available in different power driver output chips.
Current microcontrollers can serialize several parallel output lines for controlling many actuators connected to fast signals (e.g. timer outputs) using the microsecond bus. At present, known microcontrollers can support MSC up to 40 MHz with frame up to 40 bits shared between up to two devices connected and selected by the related chip-select ensuring a defined and fast data output refresh (up to 1 μs, thus the name microsecond bus). The MSC bus uses Low-Voltage Differential Signaling (LVDS, also known as TIA/EIA-644) clock and data lines from microcontroller to the devices, non-differential lines are used for chip selects and asynchronous upstream, used for diagnosis, from devices to the microcontroller. The number of chip-select outputs is a big limitation because the power dissipation limits the number of actuators controlled by a single driving circuit. For example, no more than two DC motors can be controlled by the same driving circuit. Therefore, a maximum of four DC motors could be controlled using a single microsecond bus made available by a known microcontroller.